1. Field of the Invention
This invention relates to a method, apparatus and product for biologically controlling weed trees.
More specifically, the invention relates to the biological control of red alder (Alnus rubra Bong) and similar weeds using a fungus of the genus Nectria, preferably Nectria ditissima.
2. Discussion of the Prior Art
The control of weed trees such as red alder in reforestation areas is expensive in terms of weeding costs and lost growth potential of forest areas. Chemical herbicides are used to remove the majority of alders from 15 to 40 year old conifer plantations in the Pacific Northwest of the United States and contiguous areas of Canada. For example, more than 90% of the backlog brushland clearing in British Columbia is accomplished with Vision (a trademark of Monsanto Corporation for glyphosate). Public perception of chemical herbicides is negative and there is a distinct possibility that the use of major herbicides will ultimately be banned. In fact, herbicides are presently banned on public lands in several areas including Alberta and Quebec, Canada, U.S. Forest Service (Region 3), Sweden and Switzerland. Loss of such chemicals in backlog operations and plantation clearing will present foresters with a major problem and forestry firms with substantially higher expenses because of bush clearance and replant costs. Moreover, the application of presently used herbicides is labor intensive, requiring workers to walk through plantations, remove a strip of bark around each weed tree, and paint a herbicide onto and into the wounds. The circumference of older trees is often irregular and the task may require considerable time. The rapid killing of trees using chemicals results in rapid degradation of the root nodules, which often contain a surfeit of fixed nitrogen, with consequent rapid oxidation of nitrogen. The nitrogen forms gaseous oxide gases which dissipate, becoming unavailable for replenishment of already scarce forest nitrogen stocks.